The use of communication systems through which to communication voice, and other, data is pervasive in modern society. For many, ready access to a communication system that provides for communications between users positioned at spaced-apart locations is a necessary aspect of many activities.
A communication system includes, at a minimum, a set of communication stations that are interconnected by way of the communication channel. At least one of the communication stations forms a sending station that sends the voice, or other communication, data to at least one other communication station that forms a receiving station. Communication systems of various constructions and capabilities have been developed and made available for popular usage.
A radio communication system is an exemplary type of communication system and is constructed to make use of radio channels. That is to say, in a radio communication system, the communication stations are interconnected by way of radio channels rather than channels defined upon wireline connections that extend between communication stations of a wireline communication system. Because fixed connections between the communication stations are not required in a radio communication system, communication stations of a radio communication system are positionable at locations at which wireline connections are not available while still providing for communications with other communication stations. Also, a radio communication system is amenable for implementation as a mobile communication system in which one or more of the communication stations of the set of communication stations is provided with communication mobility.
Some communication systems include fixed network infrastructures through which communication stations communicate the voice, or other communication, data. In other radio communication systems, communications are directly effectuated between the communication stations. In such communication systems, communications are effectuated free of routing by way of a communication network infrastructure. That is to say, some communication systems are infrastructure-free.
The radio channels used in a radio communication system are defined upon portions of the electromagnetic spectrum. Regulatory bodies have allocated various frequency bands of the electromagnetic spectrum for various types of communication systems. And, amongst the frequency band allocations are portions of the electromagnetic spectrum reserved for unlicensed access to users to utilize portions of the such frequency bands upon which to communicate.
In the United States, for instance, frequency bands defined at 151 and 154 MHz are made available for use pursuant to private, two-way, short-distance voice or other data communication services for the general public. The communication service for which these channels are defined is referred to as a MURS (Multi-User Radio Service). MURS communication stations are commercially available, typically constructed to be of dimensions and weights permitting their hand carriage by users. Sets of MURS communication stations are regularly utilized to communicate voice, and other, data therebetween. Because the channels are unlicensed, communications thereon are essentially unregulated. MURS communication stations utilize a mechanism by which a set of communication stations that are to be parties to a communication service or session identify themselves so that communications are carried out between the appropriate MURS communication stations.
Namely, coded squelch schemes are utilized by MURS communication stations by which to identify the respective communication stations and to facilitate communications between which the communications are to be carried out. In one conventional scheme, a continuous tone coded squelch system (CTCSS) scheme is utilized. And, in another conventional scheme, a digital coded squelch (DCS) scheme is utilized.
Another frequency band, located at 460 MHz is also allocated in the United States for unlicensed communications. Family Radio Service (FRS) communications are effectuated upon channels within this frequency band. That is to say, radio communications between FRS communication stations are carried out upon radio channels within the allocated band at the 460 MHz band. Analogous to the coded squelch schemes utilized in MURS communications, coded squelch schemes are also utilized pursuant to FRS communications.
Additionally, other types of short range, radio communication services and radio communication stations for carrying out such services, are available and utilized. Such additional radio communication services utilize, e.g., the aforementioned frequency bands, or others.
Many of the MURS and FRS communication stations include companders that operate, alternately, to compress communication data that is to be sent by a communication station and expand communication data terminating at the communication station. Companders utilized in conventional MURS and FRS communication stations are typically hardware-implemented at the baseband part of the communication station. While the conventional, hardware-implemented companders are effective in their operation, noise energy is generated as a byproduct of their operation. Filtering is required of the compressed, or expanded, values generated during their operation to remove the noise energy. The need to utilize the filters increases the circuitry size required of the circuitry of the communication station as well as increases the part count of the circuitry.
While software-implemented companders are sometimes utilized for other radio communication devices, such devices have not generally been utilized in conjunction with communication stations that utilize a coded squelch scheme, such as used in MURS and FRS communication stations.
If an improved compander could be provided for communication stations operable pursuant to coded squelch system schemes, problems associated with companders conventionally utilized in such communication stations would be avoided.
It is in light of this background information related to radio communication stations that the significant improvements of the present invention have evolved.